=begin
CGI#header was only reintroduced as alias for CGI#http_header for compatibility reasons (see #7286), it's use for this purpose is deprecated. This should be made clear in the rdoc (patch provided):

This method is an alias for #http_header, as long as the
HTML5 tag maker is not used.
NOTE: #header should no longer be used to create HTTP header
blocks, the alias is provided only for backwards compatibility.
With the HTML5 tag maker #header creates a <header> element.